Gas system for firearms



Oct. 15, 1946; w. A. SCHAICH GAS SYSTEM FOR FIREARMS Filed Sept. 5. 1944Wilbur A- fichnl' Ch 33., a. AMMMD ZMAU Patented Oct. 15, 1946 omrsoSTATES PATENT OFFICE- (Granted under the act of March 3, 1883, asamended April 30, 1928; 3'70 0. G. 757) 1 Claim.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to a gas system for a firearm and particularly toa mechanism for deriving motive power from the gases developed withinthe barrel of an automatic firearm to secure automatic operation of thebreech mechamsm.

While not limited thereto, this invention is particularly applicable tofirearms wherein the gas port in the barrel is located close to thechamber end of the barrel, resulting in the application of gases ofextremely high pressures to the gas system. Specifically a gas system inaccordance with this invention may be applied to an automatic firearmsimilar to the U. S. carbine caliber .30 M1.

The location of the gas port as near as possible to the chamber end ofthe barrel is obviously desirable from the standpoint of reduction inlength, and hence weight, of the operating rod member which transmitsforce received from the gas system to the breech mechanism to accomplishthe conventional functions of an automatic breech mechanism, namely,unlocking of the breech, extraction and ejection of the fired case, andthe loading of a fresh cartridge. With conventional gas systems however,utilizing merely a piston and cylinder, and with the piston arranged toreceive the direct impact of the gases, such location of the gas portproduces at least three well recognized undesirable features, First, theaction of the gas on the piston is extremely violent and of very shortduration thereby producing an undesirably high acceleration of thepiston and the breech mechanism with accompanying breakage of partsafter a few hundred rounds. Secondly, it is well recognized that thepressures developed by successive rounds of ammunition normally departfrom the average pressure by a substantial margin. Accordingly, a rounddeveloping slightly higher pressure would accelerate the piston andbreech mechanism at an even higher rate than would a normal round and inmany instances would cause the breech mechanism to open while thepressure in the barrel was above the value generally recognized to besafe for opening of the breech. Thirdly, the short duration of the forceexerted by the gases on a conventional piston required the accelerationof the breech mechanism to a velocity sufliciently high to insure thatthe kinetic energy imparted-to the breech mechanism in such shortduration is sufficient to carry the breech mechanism to its full recoilposition. For example, in the U. S. carbine caliber .30 M1, theoperating slide is accelerated by the piston to a maximum velocity offrom thirty to forty feet per second, which velocity is graduallyreduced during the recoil travel of the slide by the energy required toopen the bolt, extract the case, and compress the driving spring, to avalue of from six to ten feet per second at full recoil position. Thisrepresents a substantial range of velocity change during the operatingcycle and naturally requires higher shock and fatigue resistanceproperties in the moving parts.

Accordingly, it is an object of this invention to provide an improvedgas system for an automatic firearm particularly adaptable for operationby high pressure gases.

A further object of this invention is to provide a gas system for anautomatic firearm which is self compensating with respect to variationsin pressure of the operating gases supplied, to the system.

Another object of this invention is to provide a gas system for anautomatic firearm wherein the gases are permitted to operate on a movingpiston by expansion rather than by an impact blow and wherein theduration of action of the gases is substantially increased. I

A particular object of this invention is to provide an improved gassystem which may be applied to an automatic firearm similar to the U. S.carbine caliber .30 Ml which will substantially reduce the maximumvelocity of the moving parts of the breech mechanism and which willsubstantially increase the time elapsing between firing of the cartridgeand opening of the breech mechanism.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawing in which:

Fig. 1 is an elevational view, partly in section, of the elements of theimproved gas system assembled to a firearm.

Fig. 2 is a sectional view taken along the plane 2-2 of Fig. 1.

Fig. 3 is a sectional View taken along the plane 3@ of Fig. 1.

Fig. 4 is a sectional View of the cylinder member.

Referring to Fig. l a gas cylinder bracket I0 is shown secured to abarrel l in the vicinity of a gas port 2. The bracket [0 may compriseeither a separate member slipped over the barrel or may be integrallyformed with the barrel. In the depending portion of bracket it) alongitudinal hole ll is drilled parallel to the axis of the barrel. Atubular gas cylinder element is inserted into the hole H and retainedtherein by any suitable means, preferably by a press fit engagement. Aradial collar on the rear end of gas cylinder 29 bottoms against therear wall of bracket m, The top surface of the collar 2! is providedwith a fiat portion 22 which snugly engages a correspondingly flatsurface 3 provided on the bottom of barrel l and thereby serves toprevent rotational shifting of the gas cylinder 20 with respect to thebracket H3. As previously mentioned the gas cylinder 28 is hollow anddefines a gas chamber 23 which opens from the rear of gas cylinder 2%. Agas port 24 is provided thru bracket ii! and gas cylinder 20 at aposition to align with the end of barrel port 2. The port 24 ispreferably made substantially larger than port 2 in order to compensatefor any. slight misalignment of parts in assembly. A cylindrical piston36 snugly engages the interior cylindrical surface of gas chamber 23.The periphery of piston 36 is provided with a plurality of annular gasrecesses 3i which in effect produce a gas seal between the exterior ofthe piston 38 and the interior of the gas cylinder 26. Piston is alsopartially. hollow, being provided with an axial hole 3.: opening fromthe forward end of the piston. The rear end oi piston SS is solid and isarranged to lie in abutment to breech operating member 49. Operatingmember it is suitably connected to the breech mechanism (not shown) ofthe firearm and arranged to reciprocate and thereby impart the necessarymovement to such breech mechanism to produce automatic operation of theweapon. In the specific application of this invention to the U. S.carbine caliber .30 M1, breech operating member lB comprises thestandard operating rod of such weapon.

It should be understood that the full recoil stroke of operating memberto is preferably less than the length of piston 38 which is insertedwithin gas cylinder 2!), thus insuring that piston 30 is engaged in gascylinder 28 during normal operation of the firearm in all positions ofthe operating member 46. Hence no stops are needed to retain pistonwithin gas cylinder 20. An operating spring 53 is provided to returnoperating member Gil to its battery position, and piston 3i) is in turnreturned to a position Within gas cylinder it where the forward end ofpiston 33 bottoms against the base of gas chamber 23. An annular recess33 is provided about the periphery of piston 30 in such position as tolie adjacent to cylinder port 24 when piston 38 is in its batteryposition. A plurality of radial ports 3 are provided, passing thru thewall of piston 38 and located in the center of annular recess 33. Ports35 thus assure passage of the gases into the hollow portion 32 of piston33 independent of the relative angular position of piston 39 withrespect to gas cylinder 20. 1

In operation, a cartridge is fired and the bullet is driven thru thebore by the gases thus formed. After the bullet passes the barrel port2, a portion of the gases are diverted thru the barrel port 2, thecylinder port 24, and the piston ports 36 into the hollow interior 32 ofpiston 30. The

hollow interior 32 is of appreciable volume but preferably less than 25%of the barrel bore volume and hence the gases must fill such volumebefore being effective to move the piston 33 rearwardly. Thus oneelement of delay is introduced in the initiation of movement of piston30. When piston 3H begins to move rearwardly, the eifect is to misalignpiston port 34 with cylinder port 24 and in effect cut off the entry offurther gases into the gas system and trap the gases which have alreadyentered the system. Further action of the gases upon the piston is thendependent upon the expansion of the gases and accordingly a very uniformaccelerating force is applied to the piston 39, Expansion of the gaseswill continue until the ports 35 pass rearwardly out of the end ofcylinder 23 whereupon the gases will be exhausted to atmosphere. A powerstroke of any desired length may obviously be obtained by increasing thespacing between the rear end of cylinder 25 and the location of cylinderport 24. It is generally desirable to have the power strokesubstantially less than the recoil movement of the breech operatingmember in order that exhaust of the gases will occur at a substantialpressure, thereby insuring that carbon and other combustion productswill be blown out of the piston and cylinder chambers.

When a gas system constructed in accordance with this invention wasapplied to a gun similar to the U. S. carbine, caliber .30 M1, themaximum velocity attained by the moving parts in their recoil stroke wasnot over twenty feet per second. Furthermore the time elapsing betweenthe firing of a cartridge and the opening of the breech mechanism wasmore than doubled. Thus a gas system construction in accordance withthis invention not only insures longer life of moving parts of thefirearm by decreasing shock and fatigue effects but in addition providesa substantial increase in delay of breech opening, thereby insuringopening of the breech mechanism when the pressure remaining in thebarrel doesnot exceed that known in the art to be most desirable foropening of the breech and extraction of the fired case. It is obviousthat a gas system constructed in accordance with this invention is veryadaptable to large production manufacture inasmuch as all the principalparts are tubular.

I claim:

In an automatic firearm having a barrel with a gas port therein and areciprocating breech operating member. the improvement comprising a gascylinder secured to the barrel in the vicinity of the barrel gas port,said gas cylinder defining a rearwardly opening, cylindrical chamberdisposed parallel to the path of movement of said breech operatingmember, a cylindrical piston slidably and rotatably mounted within saidcylinder chamber, said piston having a forwardly opening hollow portion,the rear end of said piston arranged to abut the breech operating memberto impart rearward movement thereto, said cylinder having a gas passagetherein communicating between the barrel gas port and the interior ofsaid cylinder chamber, said piston having a reduced diameter annulargroove on its periphery located in substantial alignment with said gaspassage when said piston is in its forward position, said piston havingat least one generally radial hole in said reduced diameter annulargroove, communicating with the said hollow portion of said piston.

WILBUR A. SCI-IAICH.

